ES2971016T3 - Compound for molding sheets and fiber-reinforced composite material - Google Patents

Abstract

The present invention provides a sheet molding compound that can be suppressed in the formation of flashes during press molding, while exhibiting excellent fluidity and rapid curing properties of a matrix resin during press molding, and that allows to achieve a fiber-reinforced sheet molding compound. Composite material that has excellent mold release, mechanical characteristics and heat resistance. A sheet molding compound according to the present invention contains an epoxy resin composition and reinforcing fibers; the gelation time of the epoxy resin composition at 140° C. is 30 seconds to 140 seconds; the curing reaction start temperature of the epoxy resin composition is 70° C. to 115° C.; and if b1 is the viscosity of the epoxy resin composition at 30°C on 7 days after preparation and b2 is the viscosity of the epoxy resin composition at 30°C on 14 days after preparation, b1 and b2 satisfy b2/b1 <= 5. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Compound for molding sheets and fiber-reinforced composite material

[Technical field]

The present invention relates to a sheet molding compound and a fiber reinforced composite material.

Priority of Japanese patent application no. ° 2018-165832, filed September 5, 2018.

[Background of the art]

Due to its excellent mechanical characteristics and the like, a fiber-reinforced composite material formed by reinforcing fiber including carbon fiber and a matrix resin is widely used for aircraft, automobiles, and industrial uses. In recent years, as the use of fiber-reinforced composite material has increased, its scope of application has also expanded.

It is necessary for a matrix resin such as fiber reinforced composite to express high mechanical characteristics even in a high temperature environment. In addition, a matrix resin of a molding material (sheet molding compound (hereinafter also described as SMC), prepreg or the like) used to manufacture the fiber-reinforced composite material should have excellent molding properties.

As a matrix resin of a molding material, a resin composition containing a thermosetting resin is frequently used, with which the reinforcing fiber is excellently impregnated and which expresses excellent heat resistance after curing. As a thermosetting resin, a phenol resin, a melamine resin, a bismaleimide resin, an unsaturated polyester resin, an epoxy resin, and the like are used.

Among these, the epoxy resin composition is suitable as a matrix resin because this resin has excellent molding properties, expresses excellent heat resistance after curing, and allows a fiber-reinforced composite material prepared using the epoxy resin composition to present high mechanical characteristics.

The method of manufacturing a fiber reinforced composite material by molding a molding material includes an autoclave molding method, a filament winding molding method, a resin injection molding method, a resin injection molding method vacuum, a pressure molding method, and the like. Among these, the die casting method is in increasing demand because this method has high productivity and facilitates obtaining a fiber-reinforced composite material that is excellent in terms of design. As a molding material used in the die casting method, SMC consisting of short reinforcing fiber and a matrix resin is being actively used, because this material makes it possible to manufacture a fiber-reinforced composite material that has a complicated conformation and produces a Optimal fiber reinforced composite material for a structural element.

For the matrix resin used in SMC, the following characteristics are required.

To ensure that the carbon fiber is impregnated with the matrix resin during SMC manufacturing, the SMC matrix resin must have extremely low viscosity during SMC manufacturing.

To ensure the workability of the SMC during pressure molding, the matrix resin of the SMC must be in a B phase (a state in which the matrix resin is thickened by semi-curing and can be fluidized by heating) thickening appropriately. and having appropriate tack (pressure-sensitive adhesiveness) and moldability (flexibility) properties.

To ensure the fluidity of the matrix resin during pressure molding, the SMC matrix resin must be kept in the B phase for a long period of time (B phase stability).

To mold SMC in a short period of time at high temperature by pressure molding method, the matrix resin of SMC must be cured in a short period of time and have high heat resistance after curing.

In order to shorten as much as possible the time required for a demolding or deburring operation after pressure molding, the amount of flash formed after molding of the SMC matrix resin should be small, and the SMC should have the same or greater rigidity against mold temperature.

To obtain a carbon fiber reinforced composite material that has high mechanical characteristics and high heat resistance, it is necessary that the SMC presents high mechanical characteristics and high heat resistance after curing of the MC matrix resin.

Although the epoxy resin composition forms a cured product having excellent mechanical characteristics and heat resistance, it is difficult for the epoxy resin composition to satisfy both the rapid curing properties and the stability of the B phase.

That is, a curing agent that cures the epoxy resin in a short period of time causes the curing reaction to proceed rapidly at room temperature, the epoxy resin composition cannot be maintained in a B phase for a long period of time. On the contrary, with a curing agent that can maintain the epoxy resin composition in a B phase for a long period of time, it is difficult to cure the epoxy resin in a short period of time.

Therefore, as the matrix resin of SMC, a thermosetting resin composition obtained by diluting an unsaturated polyester resin or a vinyl ester resin with styrene is generally used. However, the thermosetting resin composition containing the unsaturated polyester resin or vinyl ester resin causes severe curing shrinkage. Furthermore, a molded product obtained from this composition contains large amounts of volatile organic compounds. Therefore, it is necessary to epoxidize the matrix resin. Compared with the thermosetting resin composition obtained by diluting the unsaturated polyester resin or vinyl ester resin with styrene, the epoxy resin composition causes less curing shrinkage. Furthermore, a molded product obtained from the epoxy resin composition contains only traces of volatile organic compounds.

As epoxy resin composition used in SMC, the following compositions are suggested.

(1) Resin composition containing an epoxy resin containing hydroxyl groups, polyol and a polyisocyanate compound (patent document 1).

(2) Resin composition containing an epoxy resin, polyol, a polyisocyanate compound, dicyandiamide and a specific imidazole compound (patent document 2).

(3) Resin composition containing an epoxy resin, an aminoalkylimidazole compound and a diazabicycloalkylene compound (patent document 3).

As epoxy resin compositions used in adhesives, the following compositions are suggested.

(4) Liquid adhesive containing an epoxy resin, a curing agent activated at a temperature of 20 °C to 100 °C and a curing agent activated at a temperature of 100 °C to 200 °C (patent document 4) .

(5) Reactive hot melt adhesive containing an epoxy resin that remains solid at room temperature, an epoxy resin that remains liquid at room temperature, linear amino-terminated polyoxypropylene, and a latent curing agent (dicyandiamide) (patent document 5).

As epoxy resin compositions used in prepregs, the following compositions are suggested.

(6) Impregnation resin composition containing an epoxy resin, a latent curing agent, a resin having a polymerizable unsaturated group and a polymerization initiator (patent document 6). (7) Epoxy resin composition containing an epoxy resin, an acid anhydride and a Lewis acid salt (boron trichloride amine complex) (patent documents 7 to 9).

As an epoxy resin composition capable of remaining in phase B stably, the following composition is suggested.

(8) Resin composition containing an epoxy resin and 2,5-dimethyl-2,5-hexamethylenediamine as a curing agent and menzendiamine (non-patent document 1).

Furthermore, patent document 10 refers to a molding material that includes an epoxy resin, an epoxy resin curing agent, a compound having a solubility parameter of 11.2 or less and a melting point of 115° C or lower, and a reinforcing fiber.

Patent document 11 relates to a sheet molding compound that is a thickened material of an epoxy resin composition, including a component (A), a component (B) and a component (C), in which component (A) is an epoxy resin that remains liquid at 25 °C, component (B) is an acid anhydride, component (C) is an epoxy resin curing agent, and in the thickened material, at least some of the epoxy groups of component (A) and at least some of the carboxyl groups derived from component (B) form ester.

Patent Document 12 describes a two-part epoxy resin composition for fiber-reinforced composite materials comprising components (A) to (D), component (D) being liquid at room temperature or a solid having a melting point. melting of 130 °C or less, wherein (A) is an epoxy resin, (B) is an acid anhydride, (C) is a compound having an average of 2.5 or more hydroxyphenyl structures in each molecule , and (D) is an organic phosphorus compound or an imidazole derivative. .

Patent Document 13 relates to a fiber reinforced composite material comprising a cured epoxy resin product obtained by curing an epoxy resin composition and a reinforcing fiber, wherein the epoxy resin composition comprises an epoxy resin (A) and a curing agent (B); 10 to 80% by mass of the curing agent (B) is 1,2-anhydride of 1,2,4-cyclohexanetricarboxylic acid; and the reinforcing fiber comprises one or more selected from the group consisting of a carbon fiber, an aramid fiber and a boron fiber.

Patent Document 14 describes an epoxy resin composition comprising an epoxy resin, a curing agent, a curing catalyst, a foaming agent and a pigment, and at least 40% by weight of a liquid epoxy resin with respect to the total amount thereof, and a total of 30 to 40 of an acid anhydride and a phenol-novolak as curing agent, in which the content of acid anhydride and phenol-novolak is 8:2 to 6: 4 by weight.

[Reference list]

[Patent bibliography!

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. S58-191723 [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. H04-88011 [Patent Document 3] International Publication PCT No. WO 2008/77836

[Patent Document 4] Japanese Unexamined Patent Application, First Publication No. H02-88684 [Patent Document 5] Japanese Unexamined Patent Application, First Publication No. H02-88685 [Patent Document 6] Japanese Patent Application Japanese Unexamined Patent, First Publication No. H02-286722 [Patent Document 7] Japanese Unexamined Patent Application, First Publication No. 2004-189811 [Patent Document 8] Japanese Unexamined Patent Application, First Publication No. No. 2004-43769 [Patent Document 9] Japanese Unexamined Patent Application, First Publication No. 2001-354788 [Patent Document 10] EP Document 3632982 A1

[Patent Document 11] Document EP 3611219 A1

[Patent Document 12] EP Document 2774939 A1

[Patent Document 13] Document EP 3133108 A1

[Patent Document 14] JP Document 2002012649

[Non-patent bibliography]

[Non-patent document 1]

Masaki Shimbo, “Epoxy Resin Handbook,” Nikkan Kogyo Shimbun, December 25, 1987 (Showa 62), pp. 155-156

[Summary of the invention]

[Technical problem]

The resin compositions described in documents (1) and (2) take advantage of a urethane reaction. Therefore due to the influence of humidity on the resin compositions, the thickening reaction rate and the state of the B phase change significantly. Therefore, it is difficult to guarantee the manipulability of SMC and the stability of the B phase.

Although the resin composition described in document (3) has fast curing properties, the storage stability of the composition is poor. Therefore, it is difficult to guarantee the manipulability of SMC and the stability of the B phase.

The liquid adhesive described in document (4) uses a curing agent (polyamine, mercaptan, isocyanate, imidazole, polyamide, poly(phenylene sulfide), a BF3 complex, ketimine, or the like) activated at a temperature of 20 ° C to 100°C. Consequently, this adhesive gels through a curing reaction as the first phase. Therefore, this adhesive has low fluidity before curing as a second phase and does not increase in volume easily and, therefore, cannot be used as a matrix resin for SMC.

The reactive hot melt adhesive described in document (5) has a high viscosity and the reinforcing fiber cannot be favorably impregnated with the adhesive. Therefore the adhesive cannot be used as SMC matrix resin.

Patent document 5 describes that when a prepreg is manufactured using the impregnation resin composition described in document (6), a solvent is incorporated into the impregnation resin composition and heating is carried out so that the solvent is removed. and partially advances a curing reaction. With this method, the solvent is easily removed. Therefore, this method is applicable to the manufacture of thin prepreg in which the resulting temperature variation of the thickness during heating and cooling is small. However, in a thick film like SMC, it is difficult to remove the solvent and a large temperature variation occurs. Therefore, a defective product is obtained in which the surface condition becomes different from the interior condition after remaining in phase B. The epoxy resin composition described in document (7) consumes a long time to remain in phase B. phase B at room temperature (23 °C). Furthermore, after phase B at room temperature, the composition has a low viscosity and extremely strong stickiness. Therefore, this composition is not suitable for SMC.

The resin composition described in document (8) contains 2,5-dimethyl-2,5-hexanediamine. Therefore, the useful life of the composition is short. Furthermore, because this resin composition contains mecendiamine, its curing properties are insufficient. Consequently, this composition is not suitable for an SMC matrix resin.

An object of the present invention is to provide a sheet molding compound that can inhibit the formation of burrs during pressure molding, allows a matrix resin to exhibit excellent fluidity and excellent rapid curing properties during pressure molding, and make it possible to obtain a fiber-reinforced composite that is excellent in terms of release properties, mechanical characteristics and heat resistance. Another object of the present invention is to provide a fiber reinforced composite material excellent in mold release properties, mechanical characteristics and heat resistance.

[Solution to the problem]

As a result of intensive studies, the inventors of the present invention have discovered that the gelation time and temperature at the beginning of the curing reaction of an epoxy resin composition have a causal relationship with the formation of flashes during the molding of a composite. for sheet molding. The inventors have also discovered that the above objects can be achieved by controlling the gelation time and temperature at the beginning of the curing reaction of the epoxy resin composition. Based on the finding, the inventors have carried out the present invention.

The present invention has the following aspects.

[1] A sheet molding compound containing an epoxy resin composition and reinforcing fiber, wherein the epoxy resin composition is a composition prepared from the following component (A), component (B), component (C) and component (D).

Component (A): an epoxy resin that remains liquid at 25 °C and 1 atm.

Component (B): an acid anhydride that remains liquid at 25 °C and 1 atm.

Component (C): a curing agent having a melting point of 40°C or greater and less than 180°C, Component (D): a curing agent having a melting point of 180°C to 300° c.

[2] The sheet molding compound according to claim 1,

wherein component (D) is at least one compound selected from dicyandiamide and imidazole based compounds.

[3] The sheet molding compound according to claims 1 or 2,

wherein component (C) comprises a curing agent having a melting point of 40°C or higher and 120°C or lower.

[4] The sheet molding compound according to any one of points [1] to [3], wherein component (B) contains 0.1 to 0.5 equivalents of acid anhydride groups with respect to 1 equivalent of epoxy groups contained in the epoxy resin composition.

[5] The sheet molding compound described in any one of points [1] to [4], wherein the epoxy resin composition contains from 1 to 30% by mass of component (B) and from 1 to 10% by mass of component (C) with respect to the total mass of the epoxy resin contained in the epoxy resin composition.

[6] The sheet molding compound according to any one of points [1] to [5], wherein the epoxy resin composition contains 0.1 to 10% by mass of component (D) with respect to the total mass of the epoxy resin contained in the epoxy resin composition.

[7] The sheet molding compound described in any one of points [1] to [6], wherein component (A) comprises a glycidylamine-based epoxy resin, and the content of the glycidylamine-based epoxy resin Glycidylamine contained in component (A) is 1% to 30% by mass with respect to the total mass (100% by mass) of component (A).

[8] The sheet molding compound described in any one of points [1] to [7], wherein the epoxy resin composition is thickened.

[9] The sheet molding compound according to any one of points [1] to [8],

wherein the viscosity of the epoxy resin composition measured as described below at 30°C, 30 minutes after preparation is 0.5 to 15 Pa.s.

[10] The sheet molding compound described in any one of points [1] to [9], wherein the viscosity of the epoxy resin composition at the beginning of the curing reaction is 0.4 to 100 Pa s, in which the viscosity is measured as described below.

[11] A method for producing a fiber reinforced composite material, comprising the step of pressure molding the sheet molding compound described in any one of points [1] to [10].

[12] A method of producing the sheet molding compound of points [1] to [10], the method comprising preparing an epoxy resin composition and impregnating reinforcing fiber with the epoxy resin composition,

wherein the epoxy resin composition is a composition prepared from the following component (A), component (B), component (C) and component (D):

Component (A): an epoxy resin that remains in a liquid state at 25 °C and 1 atm,

Component (B): an acid anhydride that remains liquid at 25 °C and 1 atm,

Component (C): a curing agent having a melting point of 40°C or greater and less than 180°C, and Component (D): a curing agent having a melting point of 180°C to 300 °C.

[13] The method according to point [12],

wherein component (D) is at least one compound selected from dicyandiamide and imidazole based compounds.

[14] The method according to points [12] or [13],

wherein component (C) comprises a curing agent having a melting point of 40°C or higher and 120°C or lower.

[15] The method according to any one of points [12] to [14],

wherein component (B) contains 0.1 to 0.5 equivalents of acid anhydride groups with respect to 1 equivalent of epoxy groups contained in the epoxy resin composition.

[16] The method according to any one of points [12] to [15],

wherein the epoxy resin composition contains 1 to 30% by mass of component (B) and 1 to 10% by mass of component (C) with respect to the total mass of the epoxy resin contained in the resin composition epoxy.

[17] The method according to any one of points [12] to [16],

wherein the epoxy resin composition contains 0.1 to 10% by mass of component (D) with respect to the total mass of the epoxy resin contained in the epoxy resin composition.

[18] The method according to any one of points [12] to [17],

wherein component (A) comprises an epoxy resin based on glycidylamine in an amount of 1% to 30% by mass.

[19] The method according to any one of points [12] to [18], the method further comprising thickening the epoxy resin composition after impregnation.

[Advantageous effects of the invention]

The sheet molding compound of the present invention can inhibit the formation of burrs during pressure molding, allows a matrix resin to exhibit excellent fluidity and excellent fast curing properties during pressure molding, and makes it possible to obtain a Fiber reinforced composite material excellent in terms of release properties, mechanical characteristics and heat resistance.

Furthermore, the fiber reinforced composite material of the present invention is a pressure molded product of the sheet molding compound of the present invention and has excellent release properties, mechanical characteristics and heat resistance.

[Description of achievements]

The following definitions of terms apply to the present specification and claims.

“Remaining liquid at 25°C” means that a substance remains liquid at conditions of 25°C and 1 atm.

“Remain a solid at 25°C” means that a substance remains a solid at conditions of 25°C and 1 atm.

“Epoxy resin” is a compound that has two or more epoxy groups in one molecule.

“Acid anhydride group” is a group having a structure in which a water molecule is removed from two acid groups (carboxyl groups, and the like).

“Acid anhydride” is a compound that has an acid anhydride group.

“Hydrogenated phthalic anhydride” is a compound in which some or all of the unsaturated carbon bonds in a benzene ring of phthalic anhydride are replaced by a saturated carbon bond.

“Thickened product” is an epoxy resin composition in phase B obtained by preparing an epoxy resin composition by mixing together the components that are to be incorporated into the epoxy resin composition and leaving the epoxy resin composition to rest in an environment of 23 ° C for 7 to 14 days from immediately after preparation.

“Sheet molding compound (SMC)” is a sheet-shaped molding material containing short reinforcing fiber and a thermosetting resin.

“Viscosity” is a value measured using a rheometer under measurement mode conditions: constant tension, strain: 300 Pa, frequency: 1.59 Hz, plate diameter: 25 mm, plate type: parallel plates and gap between plates: 0.5mm.

“Flash” means an unnecessary portion formed at the end of a molded product (SMC die-cast product) due to the outward flow of an epoxy resin composition into a gap between the upper and lower molding rows, followed by solidification during an SMC injection molding.

“Ambient temperature” means 25°C.

“A” used to describe a range of numerical values means that the range includes the numerical values listed before and after “a” as the upper limit and lower limit.

[Sheet molding compound]

The sheet molding compound of the present invention contains an epoxy resin and reinforcing fiber composition.

<Epoxy resin composition>

The epoxy resin composition contained in the SMC of the present invention is a composition prepared from a component (A): an epoxy resin that remains in a liquid state at 25 ° C and 1 atm, a component (B): an anhydride of acid that remains in a liquid state at 25 °C and 1 atm, a component (C): a curing agent that has a melting point of 40 °C or greater and less than 180 °C, and a component (D) : a curing agent that has a melting point of 180°C to 300°C.

Due to the interaction of component (B) and component (A), an ester bond is formed in the epoxy resin composition. Immediately after being prepared, the epoxy resin composition can be thickened by the reaction product of the epoxy resin and the acid anhydride. The thickened product containing the reaction product of the epoxy resin and the acid anhydride may be a matrix resin of the SMC of the present invention. Alternatively, the matrix resin of the present invention may contain the reaction product of the epoxy resin and the acid anhydride.

It is preferred that the epoxy resin composition contained in the SMC of the present invention is a thickened product of the epoxy resin composition, because then the productivity and handling capacity of the SMC can be satisfied simultaneously, the stability of the B phase of the SMC tends To be further improved (i.e., the SMC can be maintained in a B phase for a long period of time), the viscosity of the SMC changes little over time and the storage stability of the SMC tends to be excellent.

The gelation time of the epoxy resin composition at 140°C is 30 to 140 seconds, preferably 40 to 120 seconds, and more preferably 50 to 85 seconds.

When the gelation time at 140°C is 30 seconds or more, preferably 40 seconds or more, and more preferably 50 seconds or more, during pressure molding of the SMC, the fluidity of the matrix resin is improved. When the gelation time at 140 °C is 140 seconds or less, preferably 120 seconds or less, more preferably 85 seconds or less, during pressure molding of SMC, the formation of burrs can be inhibited, the demolding operation does not take a long time, and productivity can be maintained. Furthermore, when the gelation time at 140 °C is within the above range, during pressure molding of SMC, the matrix resin exhibits excellent fast curing properties.

The gelation time of the epoxy resin composition can be adjusted by formulating the epoxy resin composition.

The gelation time of the epoxy resin composition is a value measured as follows.

That is, immediately after being prepared, the epoxy resin composition is placed and sealed in an airtight container and left to rest at 23°C for 7 days. The coverslip was left for 120 seconds on a hot plate preheated to 140 °C. Seven days after preparation, the epoxy resin composition is placed on the coverslip, another coverslip is placed on it so that the epoxy resin composition is interposed between the coverslips, and the time measurement is started immediately after the composition gets between the coverslips. The upper coverslip is moved using tweezers or something similar, and the time it takes for the coverslip to stop moving is measured and adopted as the gelation time of the epoxy resin composition at 140raC.

The gelation time measured for the simple epoxy resin composition is substantially the same as the gelation time measured for the epoxy resin composition in the SMC state.

The temperature of the epoxy resin composition at the beginning of the curing reaction is 70°C to 115°C, preferably 80°C to 110°C, and more preferably 90°C to 105°C.

When the temperature at the beginning of the curing reaction is 70 °C or higher, preferably 80 °C or higher, and more preferably 90 °C or higher, during pressure molding of the SMC, the fluidity of the matrix resin. When the temperature at the beginning of the curing reaction is 115 °C or lower, preferably 110 °C or lower, and more preferably 105 °C or lower, the formation of burrs can be inhibited, the demolding operation does not take much time. time, and productivity can be maintained. Furthermore, when the temperature at the beginning of the curing reaction is within the above range, during pressure molding of the SMC, the matrix resin exhibits excellent rapid curing properties.

The temperature of the epoxy resin composition at the beginning of the curing reaction can be adjusted by formulating the epoxy resin composition.

The viscosity of the epoxy resin composition at the beginning of the curing reaction is preferably 0.4 to 100 Pa.s, more preferably 0.6 to 80 Pa.s, and even more preferably 0.8 to 50 Pa.s. .s.

When the viscosity at the beginning of the curing reaction is 0.4 Pas or greater, preferably 0.6 Pas or greater, and more preferably 0.8 Pas or greater, during pressure casting of the SMC, the formation of burrs. When the viscosity at the beginning of the curing reaction is 100 Pa s or less, preferably 80 Pa s or less, and more preferably 50 Pa s or less, during pressure molding of the SMC, the fluidity of the matrix resin is further improved.

The viscosity of the epoxy resin composition at the beginning of the curing reaction can be adjusted by formulating the epoxy resin composition.

The temperature and viscosity of the epoxy resin composition at the beginning of the curing reaction are measured values as follows.

That is, immediately after being prepared, the epoxy resin composition is placed and sealed in an airtight container and left to rest at 23°C for 7 days. Then, using a rheometer, the epoxy resin composition preserved for 7 days after preparation is heated to 25 °C and its viscosity is measured under the conditions of the measurement mode: constant tension, stress level: 300 Pa, frequency: 1.59 Hz, plate diameter: 25 mm, plate type: parallel plates, gap between plates: 0.5 mm and heating speed: 2 °C/min. The viscosity at a point in time where the curing reaction of the epoxy resin composition is about to start (i.e., at a point in time where the viscosity is about to increase rapidly) is adopted as the viscosity of the epoxy resin composition at the beginning of the curing reaction. Furthermore, the temperature at a point in time at which the curing reaction of the epoxy resin composition is about to start is adopted as the temperature of the epoxy resin composition at the beginning of the curing reaction.

The temperature at the beginning of the curing reaction measured for the simple epoxy resin composition is substantially the same as the temperature at the beginning of the curing reaction measured for the epoxy resin composition in the SMC state.

The viscosity at the beginning of the curing reaction measured for the simple epoxy resin composition is substantially the same as the viscosity at the beginning of the curing reaction measured for the epoxy resin composition in the SMC state.

The viscosity of the epoxy resin composition which is measured by the following viscometry (a) at 30 ° C, 30 minutes after preparation of the composition is preferably 0.5 to 15 Pa s, more preferably 0.5 to 15 Pa s, more preferably 0.5 to 15 Pa s, more preferably 0.5 to 10 Pa s, and even more preferably 1 to 5 Pa s.

When the viscosity measured at 30°C, 30 minutes after preparation of the composition is 0.5 Pa s or greater and more preferably 1 Pa s or greater, during the manufacturing of the SMC, the precision of a basis weight tends to be easily stabilized. (thickness of the epoxy resin composition) during coating a film with the epoxy resin composition. Furthermore, when the viscosity measured at 30 ° C, 30 minutes after preparation of the composition is 15 Pas or less, more preferably 10 Pas or less, and even more preferably 5 Pas or less, during the manufacture of the SMC using the epoxy resin composition, reinforcing fiber, and the like, the reinforcing fiber tends to be better impregnated with the epoxy resin composition. Therefore, this epoxy resin composition can be suitably used to manufacture the SMC.

Viscometry (a): Immediately after being prepared, the epoxy resin composition is placed and sealed in an airtight container and allowed to stand for 30 minutes at 23°C, and then the viscosity of the epoxy resin composition is measured at 30°C.

The viscosity of the epoxy resin composition measured by the following viscometry (b) at 30 ° C, 7 days and 14 days after preparation of the composition is preferably 5,000 to 75,000 Pa s, more preferably 6,000 to 60,000 Pa s , and even more preferably from 7,000 to 50,000 Pa s.

When the viscosity measured at 30 ° C, 7 days and 14 days after preparation of the composition is 5,000 Pa s or greater, preferably 6,000 Pa s or greater, and more preferably 7,000 Pa s or greater, the surface tack on handling of the SMC is within an appropriate range, and a cutting or rolling operation tends to be easier. When the viscosity measured at 30 ° C, 7 days and 14 days after preparation of the composition is 75,000 Pa s or less, preferably 60,000 Pa s or less, and more preferably 50,000 Pa s or less, the moldability properties of the SMC They are in an appropriate range, and handling tends to be favorable.

Viscometry (b): Immediately after preparing, the epoxy resin composition is put and sealed in an airtight container and left standing for 7 days or 14 days at 23°C, and then the viscosity of the epoxy resin composition is measured. epoxy resin at 30 °C.

When b1 represents a viscosity measured at 30 °C, 7 days after the preparation of the epoxy resin composition, and b2 represents a viscosity measured at 30 °C, 14 days after the preparation of the epoxy resin composition, b1 and b2 preferably satisfy b2/b1 < 5, more preferably satisfy b2/b1 < 4, and even more preferably satisfy b2/b1 < 3.

When b1 and b2 satisfy b2/b1 < 5, preferably satisfy b2/b1 < 4, and more preferably satisfy b2/b1 < 3, the stability of phase B of the epoxy resin composition or a thickened product of the composition of epoxy resin in the SMC. That is, the epoxy resin composition tends to remain in a B phase for a long period of time, the viscosity of the SMC changes little over time and storage stability tends to be excellent.

(Component (A))

Component (A) is an epoxy resin that remains in a liquid state at 25 °C and 1 atm.

Component (A) is a component that adjusts the viscosity of the epoxy resin composition to be within the above range so that the reinforcing fiber is better impregnated with the epoxy resin composition during the manufacturing of the SMC. Furthermore, component (A) is a component that improves the mechanical characteristics and heat resistance of the fiber reinforced composite material which is a die-cast product of the SMC. When component (A) has an aromatic ring, it is easy to adjust the mechanical characteristics of the fiber reinforced composite material to be within a desired range.

Examples of component (A) include glycidyl ether of bisphenols (bisphenol A, bisphenol F, bisphenol AD, halogen-substituted compounds of these bisphenols, and the like) (bisphenol-type epoxy resins); glycidyl ether of polyphenols obtained through a condensation reaction between phenols and an aromatic carbonyl compound; glycidyl ether of polyols (polyoxyalkylene-bisphenol A, and the like); a polyglycidyl compound derived from aromatic amines; and the like.

As component (A), a bisphenol type epoxy resin is preferred, because this resin facilitates the adjustment of the viscosity of the epoxy resin composition so that it is suitable for impregnating the reinforcing fiber with the composition, and facilitates the adjustment of the Mechanical strength characteristics of the fiber-reinforced composite material are within a desired range.

As a bisphenol-type epoxy resin, a difunctional bisphenol-type epoxy resin is preferred. Herein, "difunctional" means having two epoxy groups in one molecule.

In one aspect, a bisphenol A type epoxy resin is more preferred, because this resin allows the fiber reinforced composite material to have favorable heat resistance and favorable chemical resistance.

In another aspect, a bisphenol F type epoxy resin is more preferred, because this resin has a lower viscosity than that of the bisphenol A type epoxy resin having approximately the same molecular weight, and increases the elastic modulus of the reinforced composite material. fiber.

In yet another aspect, as component (A), an alicyclic epoxy resin is also preferred because this resin has low viscosity and can improve heat resistance and weather resistance.

Component (A) may be an epoxy resin having three or more functional groups. In particular, a trifunctional epoxy resin and a tetrafunctional epoxy resin can further improve the heat resistance of the fiber reinforced composite without significantly changing the viscosity of the epoxy resin composition. As used herein, "trifunctional" means having three epoxy groups in one molecule. “Tetrafunctional” means having four epoxy groups in one molecule.

Examples of commercial difunctional bisphenol-type epoxy resin products include the following. jER (registered trademark, the same applies in the following description) 825, 827, 828, 828EL, 828XA, 806, 806H, 807, 4004P, 4005P, 4007P and 4010P manufactured by Mitsubishi Chemical Corporation,

EPICLON (registered trademark) 840, 840-S, 850, 850-S, EXA-850CRP, 850-LC, 830, 830-S, 835, EXA-830CRP, EXA-830LVP and EXA-835LV manufactured by DIC Corporation,

EPOTORT (registered trademark) YD-115, YD-115G, YD-115CA, YD-118T, YD-127, YD-128, YD-128G, YD-128S, YD-128CA, YDF-170, YDF-2001, YDF -2004 and YDF-2005RL manufactured by NIPPON STEEL & SUMIKIN CHEMICAL CO., LTD., and the like.

Examples of commercial difunctional alicyclic epoxy resin products include the following.

CELLOXIDE (registered trademark) 2021P, 2081 and 2000 manufactured by DAICEL CORPORATION,

TTA26 manufactured by Jiangsu Tetra New Material Technology Co., Ltd., and the like.

Examples of commercial products of component (A) that have three or more functional groups include the following.

jER 152, 154, 157S70, 1031S, 1032H60, 604, 630 and 630LSD manufactured by Mitsubishi Chemical Corporation, N-730A, N-740, N-770, N-775, N-740-80M, N-770-70M, N-865, N-865-80M, N-660, N-665, N-670, N-673, N-680, N-690, N-695, N-665-EXP, N-672-EXP, N-655-EXP-S, N-662-EXP-S, N-665-EXP-S, N-670-EXP-S, N-685-EXP-S and HP-5000 manufactured by DIC Corporation,

TETRAD-X manufactured by Mitsubishi Gas Chemical Corporation, and the like.

An individual component class (A) may be used, or two or more component classes (A) may be used in combination.

In particular, when component (A) comprises a glycidylamine-based epoxy resin such as TETRAD-X, it is possible to accelerate the temporary change in viscosity of the epoxy resin composition.

That is, when the content of the glycidylamine-based epoxy resin is adjusted, the viscosity b1 or viscosity b2 described above can be controlled. Therefore, during the manufacturing of the SMC, the epoxy resin composition is in B phases more quickly and, consequently, its productivity can be increased.

As a glycidylamine-based epoxy resin, N,N,N',N'-tetraglycidyl-m-xylylenediamine is preferred because this resin facilitates the adjustment of the thickening rate and hardly deteriorates the physical properties.

When the epoxy resin composition contains a glycidylamine-based epoxy resin as component (A), the content of the glycidylamine-based epoxy resin contained in component (A) with respect to the total mass (100% by mass) of the component ( A) is preferably 1% to 30% by mass, more preferably 2% to 20% by mass, and even more preferably 3% to 15% by mass.

When the content of the glycidylamine-based epoxy resin with respect to the total mass of component (A) is 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more higher, the time it takes for the epoxy resin composition to be in phase B tends to be adequately reduced. When the content of the glycidylamine-based epoxy resin with respect to the total mass of component (A) is 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, the storage stability of the SMC tends to be favorable.

The viscosity of component (A) at 25°C may be such that the viscosity of the epoxy resin composition measured at 30°C, 30 minutes after preparation of the composition is 0.5 to 15 Pas. The viscosity of component (A) at 25°C is preferably 0.3 to 500 Pa s, and more preferably 0.3 to 400 Pa s.

The content of component (A) in the epoxy resin composition is preferably set so that the viscosity of the epoxy resin composition measured at 30°C, 30 minutes after preparation of the composition is 0.5 to 15Pa. s. The content of component (A) can be selected according to the type of component (A).

The content of component (A) in the epoxy resin composition with respect to the total mass (100% by mass) of all the epoxy resin contained in the epoxy resin composition is preferably 20% to 100% by mass, and more preferably 50% to 95% by mass.

When the content of component (A) in the epoxy resin composition is within the above range, the viscosity of the epoxy resin composition measured at 30 ° C, 30 minutes after preparation of the composition can be easily adjusted to be within of the previous range, and the reinforcing fiber is better impregnated with the epoxy resin composition. In addition, the heat resistance of the fiber reinforced composite material is further improved.

(Component (B))

Component (B) is an acid anhydride that remains liquid at 25 °C and 1 atm.

Component (B) is a component that can act on component (A) at room temperature and thickens the epoxy resin composition immediately after preparing the composition so that the epoxy resin composition is in phase B.

Because component (B) remains in a liquid state at 25°C, the components of the epoxy resin composition mix with each other uniformly and the epoxy resin composition can thicken uniformly at 25°C.

Examples of component (B) include a cyclic acid anhydride having one structure or two or more structures (cyclic acid anhydride groups) derived from the elimination of a water molecule from two acids in one molecule.

Examples of cyclic acid anhydride having a cyclic acid anhydride group in a molecule include dodecenyl-succinic anhydride, poly(adipic anhydride), poly(zelaic anhydride), methyl-tetrahydrophthalic anhydride, methyl-hexahydrophthalic anhydride, methyl-himic anhydride , hexahydrophthalic anhydride, Italic anhydride, trimellitic anhydride, 3-acetamidophthalic anhydride, 4-penten-1,2-dicarboxylic anhydride, 6-bromo-1,2-dihydro-4H-3,1-benzoxazin-2,4-dione anhydride , 2,3-anthracene-dicarboxylic anhydride, and the like.

Examples of cyclic acid anhydride having two cyclic acid anhydride groups in one molecule include glyceryl bisanhydrotrimelitate monoacetate, ethylene glycol bisanhydrotrimelitate, pyromellitic anhydride, benzophenone-tetracarboxylic anhydride, 1,2,3,4-cyclobutane-tetracarboxylic dianhydride, bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, diphenyl-3,3',4,4'-tetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 1,2,4,5 dianhydride -cyclohexane-tetracarboxylic anhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-tetralin-1,2-dicarboxylic anhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3-methyl-3-cyclohexene-1,2 anhydride -dicarboxylic, N,N-bis[2-(2,6-dioxomorpholino)ethyl]glycine, 4,4'-sulfonyldiphthalic anhydride, 4,4'-ethylenebis(2,6-morpholinedione), 4,4'-( 4,4'-isopropylidenediphenoxy)bis(phthalic anhydride), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, and the like.

As component (B), in view of the viscosity stability of the epoxy resin composition and the heat resistance or mechanical characteristics of the cured product of the epoxy resin composition, phthalic anhydride or hydrogenated phthalic anhydride which may have a substituent, and a compound represented by formula (1) or a compound represented by formula (2) is more preferred.

A single component class (B) may be used, or two or more component classes (B) may be used in combination.

The content of component (B) in the epoxy resin composition is preferably set so that the amount of acid anhydride groups with respect to 1 equivalent of epoxy groups contained in the epoxy resin composition is 0.1 to 0.5 equivalents, more preferably it is set so that the amount of acid anhydride groups is 0.1 to 0.4 equivalents, and even more preferably it is set so that the amount of acid anhydride groups is 0.1 to 0 .3 equivalents.

When the content of component (B) in the epoxy resin composition is within the above range, phase B of the epoxy resin composition advances appropriately. When the content of component (B) is set so that the amount of acid anhydride groups is 0.1 equivalent or greater with respect to 1 equivalent of epoxy groups contained in the epoxy resin composition, the epoxy resin composition reaches phase B favorably, an appropriate tack is obtained, and a carrier film favorably tends to detach from the SMC. When the content of component (B) is established so that the amount of acid anhydride groups with respect to 1 equivalent of epoxy groups contained in the epoxy resin composition is 0.5 equivalents or less, more preferably 0.4 equivalents or less, and even more preferably 0.3 equivalents or less, phase B of the epoxy resin composition advances appropriately. Therefore, favorable moldability properties are obtained and the workability of a cutting operation, a rolling operation, and the like of the SMC tends to be favorable.

The content of component (B) in the epoxy resin composition with respect to the total mass (100 parts by mass) of all the epoxy resin contained in the epoxy resin composition is preferably 1 to 30 parts by mass, more preferably 3 to 25 parts by mass, and even more preferably 5 to 20 parts by mass.

When the content of component (B) in the epoxy resin composition is within the above range, phase B of the epoxy resin composition advances appropriately. When the content of component (B) with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 1% by mass or greater, more preferably 3% by mass or greater, and even more preferably 5 mass % or greater, and even more preferably 5 mass % or greater, the epoxy resin composition favorably reaches the B phase, an appropriate tack is obtained and a carrier film tends to peel favorably from the SMC. When the content of component (B) with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 30 parts by mass or less, more preferably 25% by mass or less, and even more preferably the 20% by mass or less, the B phase of the epoxy resin composition advances appropriately. Therefore, favorable moldability properties are obtained and the workability of a cutting operation, a rolling operation, and the like of the SMC tends to be favorable.

Furthermore, when the epoxy resin composition contains, as component (B), the above-mentioned cyclic acid anhydride having two cyclic acid anhydride groups in one molecule, the content of the cyclic acid anhydride having two cyclic acid anhydride groups in one molecule with respect to the total mass (100 parts by mass) of all the epoxy resin contained in the epoxy resin composition is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass.

When the content of cyclic acid anhydride, which has two cyclic acid anhydride groups in one molecule, in the epoxy resin composition is within the above range, the fluidity of the matrix resin during pressure molding of the resin tends to be further improved. SMC. The content of the compound, having two cyclic acid anhydride groups in one molecule, with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 20 parts by mass or less, preferably 10 parts by mass or less and even more preferably 5 parts by mass or less. When the compound content is within the above range, a molding die tends to be completely filled with SMC.

(Component (C))

Component (C) is a curing agent having a melting point of 40°C or greater and less than 180°C. Component (C) is a component that functions as a curing agent for epoxy resin and acts as a catalyst to make component (A) and component (B) react with each other at room temperature during phase B in which the component (A) and component (B) react with each other.

It is preferred that component (C) remains solid at 25°C. Because component (C) remains in a solid state at 25°C, component (C) is inhibited from reacting during manufacturing of the SMC or during storage of the manufactured SMC. Therefore, the productivity, storage stability and handling ability of the SMC, the fluidity of a matrix resin during pressure molding, and the like tend to be further improved.

The melting point of component (C) is 40 °C or greater and less than 180 °C, preferably 50 °C to 170 °C, more preferably 60 °C to 150 °C, and even more preferably 65 °C to 120 °C. In another aspect, the melting point of component (C) is 40°C or greater and less than 180°C, and preferably 40°C to 120°C.

When the melting point of component (C) is 40 °C or higher, preferably 50 °C or higher, more preferably 60 °C or higher, and even more preferably 65 °C or higher, it is possible to inhibit this component from reacting quickly even at low temperature, and the molding properties and storage stability of s Mc tend to be favorable. When the melting point of component (C) is less than 180°C, preferably 170°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower, burr formation tends to be further inhibited. during SMC injection molding. Furthermore, the curing time is not excessively prolonged and tends to improve productivity.

The melting point of component (C) is a value measured using a differential scanning calorimeter (Q1000 manufactured by TA Instruments). Specifically, approximately 3 mg of a measurement sample is filled into a dedicated sealed aluminum tray and measured while heating to 300°C from -50°C at a heating rate of 10°C/min. The data obtained are represented in a graph in which the ordinates show the temperature and the abscissa the calorific value. In this graph, the melting point is taken as an inflection point at which the base line of the heating value meets the top of the peak resulting from the endothermic reaction.

The average particle diameter of component (C) is preferably 25 |im or less, and more preferably 1 to 15 |im.

When the average particle diameter of the component (C) is 25 |im or less and more preferably 15 |im or less, the component (C) has a sufficient surface area, and the content of the component (C) in the epoxy resin composition and the time it takes to cure the SMC can be reduced. In addition, component (C) is easily dispersed uniformly in the epoxy resin composition, the proportion of unreacted component (C) in the cured product can be reduced, and the physical properties of the SMC die-cast product are improved. present invention.

The average particle diameter of the component (C) is a value measured using a spray particle size distribution analyzer.

Examples of component (C) include aliphatic amine, aromatic amine, modified amine, secondary amine, tertiary amine, an imidazole-based compound, mercaptans, and the like having a melting point of 40°C or greater and less than 180° c. .

Specifically, examples of component (C) include 1H-imidazole (melting point: 90 °C), 2-methylimidazole (melting point: 144 °C), 2-undecylimidazole (melting point: 73 °C), 2 -phenylimidazole (melting point: 142 °C), 2-phenyl-4-methylimidazole (melting point: 179 °C), 1-cyanoethyl-2-methylimidazole (melting point: 55 °C), 1-cyanoethyl- 2-phenylimidazole (melting point: 108 °C), and the like.

Component (C) may also be an amine-modified compound as long as its melting point is 40°C or greater and less than 180°C. Examples of such a compound include a compound of 2-methylimidazole and phenylglycidyl ether or diglycidyl ether of bisphenol A (amine-epoxy resin adduct), and the like.

Examples of commercial products of the amine-epoxy resin adduct include PN-23 (melting point: 60 °C), PN-23J (melting point: 60 °C), PN-31 (melting point: 52 °C ), PN-31J (melting point: 52 °C), PN-40 (melting point: 76 °C), PN-40J (melting point: 76 °C), PN-50 (melting point: 83 °C), PN-50J (melting point: point: 84 °C) and P-0505 (melting point: 69 °C) manufactured by Ajinomoto Fine-Techno Co., Inc. Among these, PN-23 is preferred , PN-23J, PN-31, PN-31J and P-0505.

A single component type (C) may be used, or two or more component types (C) may be used in combination.

The content of component (C) in the epoxy resin composition with respect to the total mass (100 parts by mass) of all the epoxy resin contained in the epoxy resin composition is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 4 to 8 parts by mass.

When the content of component (C) with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 1 parts by mass or greater, more preferably 2 parts by mass or greater, and even more preferably 4 parts in mass or greater, the formation of burrs during pressure casting of SMC tends to be further inhibited. When the content of component (C) with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 10 parts by mass or less, and more preferably 8 parts by mass or less, it tends to impregnate better the reinforcing fiber with the epoxy resin composition.

(Component (D))

Component (D) is a curing agent having a melting point of 180°C to 300°C.

Since the epoxy resin composition contains component (D), the storage stability of the SMC can be improved.

The melting point of component (D) is a value measured by the same method as the method used to measure the melting point of component (C).

The average particle diameter of component (D) is preferably 25 |im or less, and more preferably 1 to 15 |im.

When the average particle diameter of the component (D) is 25 |im or less and more preferably 15 |im or less, the component (D) has a sufficient surface area, and the content of the component (D) in the epoxy resin composition and the time it takes to cure the SMC can be reduced. In addition, component (D) is easily dispersed uniformly in the epoxy resin composition, the proportion of unreacted component (D) in the cured product can be reduced, and the physical properties of the SMC die-cast product can be improved. present invention.

The average particle diameter of the component (D) is a value measured by the same method as the method used to measure the average particle diameter of the component (C).

Examples of component (D) include dicyandiamide, imidazole-based compounds having a melting point of 180°C to 300°C, and the like.

From the point of view of further improving the heat resistance of the SMC die-casting product of the present invention, among the imidazole-based compounds, 2,4-diamino-6-[2'-methylimidazolyl-( 1')]-ethyl-s-triazine (melting point: 253 °C).

Furthermore, when the epoxy resin composition also contains dicyandiamide (melting point: 206°C) as component (D), it is possible to further improve the toughness and heat resistance of the SMC die-cast product obtained from the composition. of epoxy resin without impairing the B phase forming ability of the epoxy resin composition, the stability of the B phase and the rapid curing properties.

A single component class (D) may be used, or two or more component classes (D) may be used in combination.

The content of component (D) in the epoxy resin composition with respect to the total mass (100 parts by mass) of all the epoxy resin contained in the epoxy resin composition is preferably 0.1 to 10 parts by mass, plus preferably 0.3 to 7 parts by mass, and even more preferably 1 to 5 parts by mass.

When the content of component (D) with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 0.1 parts by mass or greater, more preferably 0.3 parts by mass or greater, and even more preferably 1 parts by mass or greater, the formation of burrs during pressure molding of the SMC can be further inhibited, and the toughness and heat resistance of the pressure molded product of the SMC tend to be further improved. When the content of component (D) with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, the reinforcing fiber tends to be better impregnated with the epoxy resin composition and tends to improve the stability of phase B.

(Other components)

If necessary, the epoxy resin composition may contain components (other components) other than component (A), component (B), component (C) and component (D) described above.

Examples of other components that the above-mentioned epoxy resin composition may contain, if necessary, include a thickening accelerator, a curing accelerator for an epoxy resin, an inorganic filler, an internal release agent, a surfactant, a pigment organic, an inorganic pigment, an epoxy resin other than component (A), resins other than an epoxy resin, and the like.

As a thickening accelerator, an imidazole-based compound that remains in a liquid state at 25 °C is suitable, because this compound allows a faster B phase formation of the epoxy resin composition.

Examples of imidazole that remain in a liquid state at 25 ° C include 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, and the like.

One class of imidazoles that remains liquid at 25°C can be used individually, or two or more classes of imidazoles that remain liquid at 25°C can be used in combination.

When the epoxy resin composition contains the imidazole that remains in a liquid state at 25 ° C as a thickening accelerator, the content of the imidazole that remains in a liquid state at 25 ° C with respect to the total mass (100 parts by mass) of the entire the epoxy resin contained in the epoxy resin composition is preferably 0.01 to 0.2 parts by mass, more preferably 0.01 to 0.1 parts by mass, and even more preferably 0.03 to 0.07 mass parts.

When the content of the imidazole that remains in a liquid state at 25 ° C with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 0.01 parts by mass or greater, and even more preferably 0, 03 parts by mass or greater, the time taken for the formation of phase B of the epoxy resin composition tends to be further reduced. When the content of the imidazole that remains in a liquid state at 25 ° C with respect to the total mass of all the epoxy resin contained in the epoxy resin composition is 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, and even more preferably 0.07 parts by mass or less, tends to improve the stability in the B phase of the epoxy resin composition. As a curing accelerator of the epoxy resin, a urea compound is preferred because this compound further improves the mechanical characteristics (flexural strength and flexural modulus) of the fiber reinforced composite material.

Examples of the urea compound include 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea , 2,4-bis(3,3-dimethylureido)toluene, 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea), and the like. Furthermore, in order to improve the storage stability of the curing agent, the epoxy resin composition may also contain a compound (for example, boric acid, a boric acid ester compound, or the like) coordinated with an amine. Examples of commercial products of the compound coordinated with an amine include L-070E (manufactured by SHIKOKU CHEMICALS CORPORATION, a mixture of diglycidyl ether of bisphenol A, a phenol-novolac resin and a boric acid ester compound), and the like.

Examples of inorganic filler include calcium carbonate, aluminum hydroxide, clay, barium sulfate, magnesium oxide, glass powder, hollow glass beads, Aerosil, and the like.

When the epoxy resin composition contains the inorganic filler, it is possible to suppress curing shrinkage.

Examples of internal release agents include carnauba wax, zinc stearate, calcium stearate, and the like.

When the epoxy resin composition contains the internal release agent, the SMC is released more easily after molding.

As a surfactant, in view of the migration to the surface of the SMC, a liquid surfactant is preferred, and a liquid surfactant containing an alkyl chain having 12 to 18 carbon atoms is more preferred.

When the epoxy resin composition contains a surfactant, a M<c>carrying film can be better released. Additionally, it is possible to reduce voids in the SMC.

Examples of epoxy resin other than component (A) include an epoxy resin that remains in a semi-solid state or solid state at 25°C. As an epoxy resin other than component (A), an epoxy resin having an aromatic ring is preferred, and a difunctional epoxy resin is more preferred. Additionally, in addition to the difunctional epoxy resin, for the purpose of improving the heat resistance of the SMC pressure-molded product or controlling the viscosity of the epoxy resin composition, various epoxy resins can be incorporated into the epoxy resin composition herein. invention. To improve heat resistance, a multifunctional epoxy resin, a novolac type epoxy resin or an epoxy resin having a naphthalene skeleton is effective.

Examples of resins other than epoxy resin include a thermoplastic resin, a thermoplastic elastomer and an elastomer other than a thermoplastic elastomer, and the like. By changing the viscoelasticity of the epoxy resin composition, these resins cause the epoxy resin composition to have an appropriate viscosity, an appropriate storage modulus and appropriate thixotropic properties and improve the toughness of the cured product of the epoxy resin composition.

As a resin other than epoxy resin, fine core-shell type elastomer particles are preferred. Examples of commercial products of core-shell type elastomer fine particles include “METAb LEN (registered trademark)” (manufactured by Mitsubishi Chemical Corporation), “STAPHYLOID (registered trademark)” (manufactured by Aica Kogyo Co., Ltd.) , “PARALOID (registered trademark)” (manufactured by The Dow Chemical Company), and the like. Core-shell type elastomer fine particles are also available as a masterbatch type epoxy resin pre-dispersed in an epoxy resin. Examples of such core-shell type elastomer dispersion epoxy resin include “KANEACE (registered trademark, the same applies to the following description)” (manufactured by Kaneka Corporation), “ACRYSET (registered trademark) BP series” (manufactured by NIPPON SHOKUBAI CO., LTD.), and the like.

As a resin other than epoxy resin, a core-shell type elastomer dispersion epoxy resin is preferred to be used, because this resin can reduce the time required to prepare the epoxy resin composition and allows rubber particles to be favorably dispersed in the composition. of epoxy resin. Specifically, it is possible to use the KANEACE MX series manufactured by Kaneka Corporation, such as MX-113, MX-120, MX-125, MX-128, MX-130, MX-135, MX-136, MX-156, MX -153, MX-257, MX-150, MX-154, MX-960, MX-170, MX-267, MX-965, MX-217, MX-416, MX-451, MX-553, MX-710 , MX-714, and the like.

One kind of resin other than epoxy resin may be used individually, or two or more kinds of resin other than epoxy resin may be used in combination.

(Method for preparing an epoxy resin composition)

The epoxy resin composition can be prepared by the method known in the related art. For example, the epoxy resin composition can be prepared by mixing the components together at a time, or prepared by preparing a masterbatch in advance by appropriately dispersing component (C), component (D) being used if necessary, and the like in component (A) and mixing the mother mixture with the rest of the components. Furthermore, when the internal temperature of the system increases due to shear heating caused by kneading, and the like, it is preferred to implement a method to inhibit the temperature increase during kneading, such as controlling the kneading speed or cooling the preparation oven. or the kneading oven.

Examples of kneading devices include an electric mortar, a grinder, a planetary mixer, a dissolver, a triple cylinder, a kneader, a universal stirrer, a homogenizer, a homodispenser, a ball mill, a bead mill, and the like. . Two or more kinds of kneading devices may be used in combination.

(Effects of epoxy resin composition)

Because the epoxy resin composition contained in the SMC of the present invention contains component (A), the viscosity of the composition can be reduced immediately after preparation of the composition. For example, the viscosity of the epoxy resin composition measured at 30°C, 30 minutes after preparation of the composition may be 15Pas or less. Therefore, the composition has excellent reinforcing fiber impregnation properties and can be suitably used to manufacture the SMC.

Furthermore, the epoxy resin composition contained in the SMC of the present invention can be thickened in a short period of time immediately after preparation of the composition. For example, the viscosity of the epoxy resin composition measured at 30 ° C, 7 days after preparation of the composition may be 5,000 to 75,000 Pa.s. Therefore, it is possible to suppress surface tack when handling SMC and obtain appropriate moldability properties and favorable workability.

Furthermore, after thickening, the epoxy resin composition contained in the SMC of the present invention can maintain viscosity for a long period of time. For example, the viscosity of the epoxy resin composition measured at 30°C, 14 days after preparation of the composition may be 5,000 to 75,000 Pa.s. Therefore, the composition has excellent tack properties and moldability after the formation of phase B, and the stability of phase B is excellent.

Furthermore, because the epoxy resin composition contained in the SMC of the present invention contains component (A), the rigidity, mechanical characteristics and heat resistance of the SMC die-cast product can be further improved.

<Reinforcing fiber>

As the reinforcing fiber to be incorporated into the SMC of the present invention, various fibers can be adopted depending on the use and purpose of use of the SMC. Examples of fibers include carbon fiber (including graphite fiber; the same applies to the following description), aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, tungsten carbide fiber, carbon fiber. glass, and the like. Among these, in view of the mechanical characteristics of the fiber reinforced composite material, carbon fiber and glass fiber are preferred, and carbon fiber is particularly preferred.

Typically, the reinforcing fiber is used in the form of a filament ribbon of reinforcing fibers made up of 1,000 to 60,000 individual filaments. Some of the SMCs contain reinforcing fiber that is in the form of a filament ribbon of reinforcing fibers, while others contain reinforcing fiber that is in the form of independent filament ribbons made up of fewer fibers. Typically, the reinforcing fiber in SMC is in the form of filament tapes made up of fewer fibers.

As the reinforcing fiber, filament tapes of staple reinforcing fibers consisting of short fiber are preferred. The average length of the reinforcing fiber is preferably 0.3 to 10 cm, more preferably 1 to 5 cm, and even more preferably 2.5 to 5 cm.

When the average length of the reinforcing fiber is within the above range, an SMC having well-balanced molding properties and mechanical characteristics is obtained. When the average length of the reinforcing fiber is 0.3 cm or more, more preferably 1 cm or more, and even more preferably 2.5 cm or more, a fiber-reinforced composite material having higher characteristics tends to be easily obtained. mechanical. When the average length of the reinforcing fiber is 10 cm or less, and more preferably 5 cm or less, the fluidity of the matrix resin during pressure molding tends to be further improved.

It is most preferred that the reinforcing fiber in the SMC be a sheet-like substance made up of ribbons of filaments of chopped reinforcing fibers that are stacked in a two-dimensional and random manner.

<Method for making sheet molding compound>

For example, SMC is manufactured by sufficiently impregnating a sheet-like substance formed by filament ribbons of cut reinforcing fibers with the above-mentioned epoxy resin composition and thickening the epoxy resin composition.

As a method of impregnating the sheet substance of the staple fiber filament tape with the epoxy resin composition, various methods can be adopted.

methods known in the related art according to the shape of the reinforcing fiber. For example, the following method can be adopted.

Two sheets of films uniformly coated with an epoxy resin composition are prepared. Tapes of chopped reinforcing fiber filaments are randomly dispersed on the surface of one of the films coated with the epoxy resin composition, thereby preparing a sheet-like substance of the chopped reinforcing fiber filament tapes. The epoxy resin composition-coated surface of the other film is bonded to the surface of the sheet-like substance of the cut reinforcing fiber filament tapes, and the obtained laminated material is pressed so that the Cut reinforcing fibers are impregnated with the epoxy resin composition, thereby obtaining a precursor to the sheet molding compound (SMC precursor).

When the SMC precursor obtained by impregnating the filament ribbons of chopped reinforcing fibers with the epoxy resin composition is maintained as is for several days to tens of days at a temperature of about room temperature to 60 ° C or for several seconds to tens of minutes at a temperature of about 60 ° C to 80 ° C, an epoxy group, which is contained in component (A) in the epoxy resin composition and other epoxy resins optionally mixed in the composition, and a group carboxyl derived from component (B) cause an esterification reaction and, consequently, the epoxy resin composition is formed in phase B (it thickens). By thickening the epoxy resin composition in this way, the SMC with suppressed surface tack is obtained, which is suitable for a molding operation.

It is preferred to select the reaction conditions for the epoxy group contained in the epoxy resin and the carboxyl group derived from component (B) so that the viscosity of the epoxy resin composition obtained after the esterification reaction is measured at 30 ° C or the viscosity of the epoxy resin composition at the beginning of the curing reaction is within the range described above.

<Action and effect>

In the SMC of the present invention containing the epoxy resin composition described so far that has a gelation time of 30 to 140 seconds at 140 ° C and has a temperature at the beginning of the curing reaction of 70 ° C to 115 ° C, a matrix resin exhibits excellent fluidity during pressure molding of SMC and the formation of burrs can be inhibited. Furthermore, in the SMC of the present invention, a matrix resin exhibits excellent fast curing properties during pressure molding of the SMC, that is, a high curing speed is obtained during pressure molding. Therefore, the SMC remains in a die for a short period of time and thus the productivity of the fiber reinforced composite material is improved. In particular, when the epoxy resin composition containing component (A), component (B) and component (C) described above is used, a thickened product of the epoxy resin composition is obtained which is further improved in terms of to stickiness and moldability properties after obtaining the B phase formation, and the handling ability of the SMC is further improved.

Furthermore, according to the SMC of the present invention that satisfies b2/b1 < 5, where b1 represents a viscosity measured at 30 ° C, 7 days after preparation of the composition and b2 represents a viscosity measured at 30 ° C, 14 days after preparation of the composition, the stability of the B phase of the SMC is excellent, the SMC tends to remain in a B phase for a long period of time, the viscosity of the SMC changes little over time and tends storage stability of SMC to be excellent.

Furthermore, the SMC of the present invention contains the epoxy resin composition that produces a cured product excellent in terms of rigidity, mechanical characteristics and heat resistance. Therefore, from the SMC of the present invention, it is possible to obtain a fiber-reinforced composite material that is excellent in terms of release properties, mechanical characteristics and heat resistance.

[Fiber reinforced composite]

The fiber reinforced composite material of the present invention is a pressure molded product of the SMC of the present invention.

The fiber reinforced composite material of the present invention can be manufactured by pressure molding the SMC of the present invention and curing the epoxy resin composition contained in the SMC of the present invention. Examples of the method for manufacturing the fiber reinforced composite material of the present invention include the following method.

A sheet of the SMC of the present invention, or a substance consisting of a plurality of sheets of the stacked SMC of the present invention, is placed between a pair of rows. The SMC is pressure molded (compression molded) so that the epoxy resin composition contained in the SMC is cured, thereby obtaining a pressure molded product of the SMC, that is, a fiber reinforced composite material that is a cured SMC product. As a core material, a honeycomb structure, such as corrugated cardboard, may be used, and the SMC of the present invention may be arranged on one or both surfaces thereof.

Herein, for example, laminating two sheets of SMC is described as “2-layer lamination.”

Die casting is preferably carried out at a temperature of 120°C to 230°C.

Pressure molding is preferably carried out for 2 to 60 minutes.

<Action and effect>

The fiber reinforced composite material of the present invention described so far is a pressure molded product of the SMC of the present invention. Therefore, the formation of burrs during pressure casting is inhibited. As a result, the fiber reinforced composite material of the present invention is excellent in workability, release properties, mechanical characteristics and heat resistance.

[Other realizations]

The present invention is not limited to the embodiments described above and may be modified in various ways within the scope described in the claims. Embodiments, which are obtained by suitably combining the technical means described in the above embodiments with other embodiments, are also included in the technical scope of the present invention.

[Examples]

Later herein, the present invention will be described more specifically based on examples, but the present invention is not limited thereto.

<Components>

(Component (A))

jER828: Bisphenol A type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, viscosity at 25 °C: 12 Pas)

jER807: bisphenol F type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, viscosity at 25 °C: 3 Pa s)

jER827: Bisphenol A type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, viscosity at 25 °C: 9 Pa s)

TETRAD-X: N,N,N',N'-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Chemical Corporation, viscosity at 25 °C: 2 Pa s)

(Component (B))

HN-2200: 3-methyl-1,2,3,6-tetrahydrophthalic anhydride or 4-methyl-1,2,3,6-tetrahydrophthalic anhydride (manufactured by Hitachi Chemical Co., Ltd., viscosity at 25 °C: 75 MPas)

(Component (C))

PN-23J: amine-epoxy resin adduct (manufactured by Ajinomoto Fine-Techno Co., Inc., melting point: 59 °C, average particle diameter: 5 |im).

PN-31J: amine-epoxy resin adduct (manufactured by Ajinomoto Fine-Techno Co., Inc., melting point: 52 °C, average particle diameter: 5 |im).

P-0505: amine and epoxy resin adduct (manufactured by SHIKOKU CHEMICALS CORPORATION, melting point: 69 °C, average particle diameter: 5 |im).

(Component (D))

2MZA-PW: 2,4-diamino-6-[2'-methylimidazole-(1')]-ethyl-s-triazine (manufactured by SHIKOKU CHEMICALS CORPORATION, melting point: 253 °C, average particle diameter: approx. 4 |im) DICYANEX 1400F: dicyandiamide (manufactured by Air Products and Chemicals, Inc., melting point: 206 °C, average particle diameter: 4 |im)

(Other components)

L-070E: a mixture of diglycidyl ether of bisphenol A, a phenol-novolac resin and a boric acid ester compound (manufactured by SHIKOKU CHEMICALS CORPORATION).

Carbon black (inorganic pigment): Mitsubishi Carbon Black #1000 (manufactured by Mitsubishi Chemical Corporation)

(Preparation of the mother mixture)

Component (C) and component (D) were each mixed with jER828 in a ratio of 1:1 (mass ratio). A maz ERUSTAR planetary deaerator agitator (manufactured by KURa Bo INDUSTRIES LTD.) was used for mixing.

Each of the mixtures obtained was kneaded using a triple cylinder, thus obtaining a master mixture.

[Examples 1 to 8 and 10 to 13 and comparative examples 1 and 2]

<Preparation of epoxy resin composition>

According to the formulation shown in Tables 1 to 3, the components were weighed and placed in a flask. For PN-23J, PN-31J, P-0505, carbon black, 2MZA-PW and DICYANEX 1400F, the masterbatch was used. The weighed components placed in the flask were stirred uniformly at room temperature, thereby obtaining an epoxy resin composition. A MAZERUSTAR planetary deaerator agitator (manufactured by KURABO INDUSTRIES LTD.) was used for agitation.

The epoxy resin composition obtained was measured and evaluated as follows. The results are shown in Tables 1 to 3.

(Viscometry 1: isothermal viscosity measurement)

Immediately after preparation, the epoxy resin composition was placed and sealed in an airtight container and stored by letting it sit in a room at 23°C in a location protected from direct sunlight. Thirty minutes, 7 days and 14 days after the preparation of the epoxy resin composition, the viscosity of the composition was measured as shown below.

The plate of a rheometer (manufactured by Thermo Fisher Scientific, HAAKEMARS40) was preheated to 30 °C and kept as is until the temperature stabilized. After the temperature was found to be stable, the epoxy resin composition was isolated on the plate, the gap was adjusted, then the plate was left as it was until the normal force was 3 N or less, and then started the measurement under the following conditions. For 10 minutes, 10 points were measured and the final measurement value was adopted as viscosity.

■ Measurement mode: constant voltage,

■ Stress level: 300 Pa,

■ Frequency: 1.59 Hz,

■ Plate diameter: 25 mm,

■ Plate type: parallel plates,

■ Gap between plates: 0.5 mm.

The viscosity of the epoxy resin composition measured at 30°C, 30 minutes after preparation of the composition is a measure of the impregnation properties during impregnation of the reinforcing fiber with the epoxy resin composition. The lower the viscosity, the better the impregnation properties.

The viscosity of the epoxy resin composition measured at 30°C, 7 days after preparation of the composition is a measure to determine whether the epoxy resin composition has become a thickened product with appropriate B phase formation that allows the SMC demonstrates appropriate tack or moldability properties. Specifically, when the viscosity is in a range of 5,000 to 75,000 Pas, it is determined that the epoxy resin composition has been converted into an appropriate B-phase forming thickened product.

The viscosity of the epoxy resin composition measured at 30 °C, 14 days after preparation of the composition is a measure to determine whether the epoxy resin composition can be maintained in a B phase for a long period of time (viscosity of the epoxy resin composition). phase B). Specifically, when the viscosity is in a range of 5,000 to 75,000 Pa s, the stability of phase B is determined to be favorable.

(Viscometry 2: measurement of viscosity under heating conditions)

Immediately after preparation, the epoxy resin composition was placed and sealed in an airtight container and stored by letting it sit in a room at 23°C in a location protected from direct sunlight. The viscosity of the epoxy resin composition was measured as follows 7 days and 14 days after preparation of the composition. The viscosity measured at a point in time at which the curing reaction of the epoxy resin composition is about to begin is described as "viscosity at the beginning of the curing reaction." The temperature measured at a point in time at which the curing reaction of the epoxy resin composition is about to start is described as "temperature at the beginning of the curing reaction."

The plate of a rheometer (manufactured by Thermo Fisher Scientific, HAAKEMARS40) was preheated to 25 °C and kept as is until the temperature stabilized. After the temperature was found to be stable, the epoxy resin composition was isolated on a plate, the gap was adjusted, and then the measurement was started under the following conditions.

■ Measurement mode: constant voltage,

■ Stress level: 300 Pa,

■ Frequency: 1.59 Hz,

■ Plate diameter: 25 mm,

■ Plate type: parallel plates,

■ Gap between plates: 0.5 mm,

■ Heating rate: The epoxy resin composition was heated at 2 °C/min from 25 °C to a temperature at which the curing reaction of the composition was about to start (i.e., a temperature at which the viscosity increased rapidly).

Viscosity measured under heated conditions is a measure of the fluidity of a matrix resin which is, in other words, the epoxy resin composition during SMC pressure casting, and a measure of the amount of flash that is formed. during pressure molding.

The temperature at the beginning of the curing reaction was evaluated based on the following evaluation criteria. When a sample was graded “A,” it was determined that the matrix resin had favorable flowability and the amount of flash formed during pressure casting is small.

A (favorable): The temperature at the beginning of the curing reaction of the epoxy resin composition measured after 7 days and 14 days is 70 °C to 115 °C.

B (defective): The temperature at the beginning of the curing reaction of the epoxy resin composition measured after 7 days and 14 days is less than 70 °C or more than 115 °C.

(Measurement of gelation time)

Immediately after being prepared, the epoxy resin composition was placed and sealed in an airtight container and left to stand in a room at 23°C for 7 days in a location protected from direct sunlight. A coverslip (manufactured by Matsunami Glass Ind., Ltd.) having a thickness of 0.13 to 0.17 mm was left for 120 seconds on a hot plate preheated to 140°C. Then, the epoxy resin composition preserved for 7 days after preparation was placed on the coverslip, another coverslip was placed on it so that the epoxy resin composition was interposed between the coverslips, and the time measurement was started immediately. after the composition was interposed between the coverslips. The top coverslip was moved using tweezers, and the time it took for the coverslip to stop moving was measured and adopted as the gelation time of the epoxy resin composition at 140°C.

The measured gelation time is a measure of the time required to mold the SMC. Additionally, gelation time is a measure of burr formation during pressure casting of SMC.

A (favorable): Gelation time is 50 to 85 seconds.

B (not bad): Gelation time is 30 seconds or more and less than 50 seconds, or more than 85 seconds and 140 seconds or less.

C (defective): gelation time is less than 30 seconds or more than 140 seconds.

(SMC manufacturing)

Using a doctor blade, a carrier film composed of polyethylene was coated with the epoxy resin composition with a coating weight of 360 g/m2. In this way, two sheets of films were prepared. On the surface coated with epoxy resin composition of one of the films, ribbons of chopped carbon fiber filaments were dispersed, which were obtained by cutting a ribbon of carbon fiber filaments consisting of 3,000 filaments (manufactured by Mitsubishi Chemical Corporation, TR50S 3L) at an average length of 25 mm, so that the basis weight of the carbon fiber was substantially uniform at 1,080 g/m2 and the fiber direction of the carbon fiber was random. In this way a sheet-shaped substance was obtained.

The epoxy resin composition-coated surface of the other film was bonded to the surface of the sheet substance prepared as above so that ribbons of chopped carbon fiber filaments were interposed between the epoxy resin compositions. The laminated material obtained was pressed by passing it between cylinders so that the ribbons of cut carbon fiber filaments were impregnated with the epoxy resin composition, thus obtaining an SMC precursor.

The obtained SMC precursor was left standing at room temperature for 7 days so that the epoxy resin composition in the SMC precursor was sufficiently thickened, thereby obtaining an SMC of 280 mm (length) x 280 mm (width). which contained a composition of epoxy resin and reinforcing fiber. <Manufacturing of fiber reinforced composite material>

The SMC was laminated in 2 layers, thus obtaining a laminated material. A 300 mm (length) x 300 mm (width) x 2 mm (thickness) molding die was loaded with the laminated material at a loading ratio of 65% (ratio of SMC area to die area), and the SMC was heated and compressed for 5 minutes under the conditions of a die temperature of 140 ° C and a pressure of 4 MPa so that the epoxy resin composition was cured, thereby obtaining a fiber-reinforced composite material in 300mm x 300mm flat plate shape having a thickness of about 2mm (CFRP molding plate).

The obtained fiber reinforced composite material was measured and evaluated as follows. The results are shown in tables 1 to 3.

(burr formation evaluation)

The burr formation rate during the fabrication of the fiber-reinforced composite material was calculated from the following equation (I).

Burr formation rate = (X - Y) / (X) x 100 ... (I)

(In equation (I),

When the number of burrs formed in a molding die is small, the burrs inside can be removed in a short period of time after molding. Consequently, the molding cycle can be shortened.

Burr formation was evaluated based on the following evaluation criteria.

A (favorable): The burr formation rate is less than 6%.

B (defective): The burr formation rate is 6% or higher.

(Mechanical characteristics evaluation 1: 3-point bending test)

Twelve test specimen sheets with a width of 25 mm, a length of 100 mm and a thickness of approximately 2 mm were cut from the fiber-reinforced composite material. Using a universal testing apparatus (manufactured by Instron, INSTRON 5965), the flexural strength, flexural modulus and bending elongation at break were measured according to JIS K 7017 under the following conditions, and the average was determined of the 12 sheets.

■ Crosshead speed; 1 mm/minute,

■ Gap Length: Established by actually measuring the thickness of the fiber reinforced composite material and multiplying the thickness by 16 (unit: mm).

(Evaluation of mechanical characteristics 2: tensile test)

Six test specimen sheets with a width of 25 mm, a length of 250 mm and a thickness of approximately 2 mm were cut from the fiber-reinforced composite material. Using a universal testing apparatus (manufactured by Instron, INSTRON 4482), the tensile strength and tensile modulus were measured according to JIS K 7164 under the following conditions, and the average of the 6 sheets was determined.

■Separation length: 150mm,

■Strain gauge: KFGS-20-120-C1-11L1M2R,

■Caliber length: 20mm,

■Data recording device: KYOWA EDX100A,

■Crosshead speed; 2mm/min.

(Heat resistance evaluation: heat resistance test)

The fiber reinforced composite material was processed into a 55 mm (length) x 12.5 mm (width) specimen and measured at a measurement frequency of 1 Hz and a heating rate of 5 °C/min using a rheometer. (TA Instrument, Inc., ARES-RDA). The temperature at which a peak appears on a tan-temperature curve 8 was defined as the glass transition temperature and the heat resistance was evaluated based on the following evaluation criteria.

A (favorable): The glass transition temperature is 140 °C or higher.

B (defective): the glass transition temperature is less than 140 °C.

[Table 1]

______ _____ [Table 2]

[Table 3]

The epoxy resin compositions used in Examples 1 to 8 and 10 to 13 were appropriately subjected to B phase formation 7 days after preparation of the compositions, and exhibited appropriate tack and moldability properties when the compositions were They became the s Mc. Furthermore, the tack and moldability properties of the compositions presented 14 days after preparation of the compositions were not significantly different from those presented 7 days after preparation of the compositions. Furthermore, the fluidity of the matrix resin during pressure molding of the SMC was equivalent to the fluidity of the compositions. As is evident from the results of viscosity measurement under heating conditions, the fluidity is stable.

In the SMC obtained in Examples 1 to 8 and 10 to 13, the gelation time of the epoxy resin composition was 30 to 140 seconds, and the matrix resin exhibited favorable rapid curing properties. Therefore, by manufacturing a fiber-reinforced composite material, the SMC could be molded in a short period of time.

In addition, few burrs were formed on die-cast products (fiber-reinforced composite material) of the SMC obtained in Examples 1 to 8 and 10 to 13, which demonstrated that the SMC obtained in Examples 1 to 13 has high productivity. As evident from the gel time measurement results, the fast curing properties and productivity are excellent.

From the SMC obtained in Examples 1 to 8 and 10 to 13, fiber-reinforced composite materials excellent in terms of mechanical characteristics and heat resistance were obtained.

The tack and moldability properties of Comparative Example 1 and its handleability resulting from the temporal change of the tack and moldability properties were substantially the same as those of the examples. However, in Comparative Example 1, large amounts of burrs were formed during the molding of the SMC.

The gelation time and temperature at the beginning of the curing reaction of the epoxy resin composition in Comparative Example 1 were significantly different from those of Examples 1 to 8 and 10 to 13, which showed that the curing properties of The composition of epoxy resin is correlated with the amount of burrs formed. As is evident from the results of the examples and comparative examples, appropriately controlling the curing properties of the epoxy resin composition, that is, controlling the gelation time and temperature at the beginning of the curing reaction of the composition of epoxy resin, the molding properties of the SMC could be changed.

[Industrial applicability]

The sheet molding compound of the present invention inhibits the formation of burrs during pressure molding. Furthermore, the epoxy resin composition used to make the sheet molding compound is a material that has excellent reinforcing fiber impregnation properties, has excellent tack properties and moldability after B phase formation, has a excellent stability in the B phase (flowability during pressure casting), exhibits excellent rapid curing properties during heating (remains in a row for a short period of time during pressure casting), produces a pressure molded product with strength excellent heat resistance and has extremely high productivity. Furthermore, due to its excellent mechanical characteristics and heat resistance after curing, the sheet molding compound of the present invention is suitable as raw material for structural parts for industries and automobiles.

Claims (19)

Yo. Sheet molding compound, comprising: an epoxy resin composition; and reinforcing fiber, wherein the epoxy resin composition is a composition prepared from the following component (A), component (B), component (C) and component (D), component (A): an epoxy resin that remains in a liquid state at 25 °C and 1 atm, component (B): an acid anhydride that remains in a liquid state at 25 °C and 1 atm, and component (C): a curing agent that has a melting point measured according to the description of 40 °C or higher and less than 180 °C, component (D): a curing agent having a melting point measured according to the description of 180 °C to 300 °C. 2. Sheet molding compound according to claim 1, wherein component (D) is at least one compound selected from dicyandiamide and imidazole based compounds. 3. Sheet molding compound according to claims 1 or 2, wherein component (C) comprises a curing agent having a melting point of 40°C or higher and 120°C or lower. 4. Sheet molding compound according to any one of claims 1 to 3, wherein component (B) contains 0.1 to 0.5 equivalents of acid anhydride groups with respect to 1 equivalent of epoxy groups contained in the epoxy resin composition. 5. Sheet molding compound according to any one of claims 1 to 4, wherein the epoxy resin composition contains 1 to 30% by mass of component (B) and 1 to 10% by mass of component (C) with respect to the total mass of the epoxy resin contained in the resin composition epoxy. 6. Sheet molding compound according to any one of claims 1 to 5, wherein the epoxy resin composition contains 0.1 to 10% by mass of component (D) with respect to the total mass of the resin epoxy contained in the epoxy resin composition. 7. Mass for molding sheets according to any one of claims 1 to 6, wherein component (A) comprises an epoxy resin based on glycidylamine, and The content of the glycidylamine-based epoxy resin contained in component (A) is 1% to 30% by mass with respect to the total mass (100% by mass) of component (A). 8. Sheet molding compound according to any one of claims 1 to 7, wherein the epoxy resin composition is thickened. 9. Sheet molding compound according to any one of claims 1 to 8, wherein the viscosity of the epoxy resin composition measured according to the description at 30 ° C, 30 minutes after preparation is 0.5 to 15 Pa s. 10. Sheet molding compound according to any one of claims 1 to 9, wherein the viscosity of the epoxy resin composition at the beginning of the curing reaction is 0.4 to 100 Pa.s, wherein the viscosity is measured as described in the description. 11. Method for producing a fiber reinforced composite material, comprising the step of pressure molding the sheet molding compound according to any one of claims 1 to 10. 12. Method of producing the sheet molding compound according to claims 1 to 10, the method comprising preparing an epoxy resin composition and impregnating reinforcing fiber with the epoxy resin composition, wherein the epoxy resin composition is a composition prepared from the following component (A), component (B), component (C) and component (D): component (A): an epoxy resin that remains in a liquid state at 25 °C and 1 atm, component (B): an acid anhydride that remains in a liquid state at 25 °C and 1 atm, component (C): a curing agent that has a melting point measured according to the description of 40 °C or higher and less than 180 °C, and component (D): a curing agent having a melting point measured according to the description of 180 °C to 300 °C. 13. Method according to claim 12, wherein component (D) is at least one compound selected from dicyandiamide and imidazole based compounds. 14. Method according to claims 12 or 13, wherein component (C) comprises a curing agent having a melting point of 40°C or higher and 120°C or lower. 15. Method according to any one of claims 12 to 14, wherein component (B) contains 0.1 to 0.5 equivalents of acid anhydride groups with respect to 1 equivalent of epoxy groups contained in the epoxy resin composition. 16. Method according to any one of claims 12 to 15, wherein the epoxy resin composition contains 1 to 30% by mass of component (B) and 1 to 10% by mass of component (C) with respect to the total mass of the epoxy resin contained in the resin composition epoxy. 17. Method according to any one of claims 12 to 16, wherein the epoxy resin composition contains 0.1 to 10% by mass of component (D) with respect to the total mass of the epoxy resin contained in the epoxy resin composition. 18. Method according to any one of claims 12 to 17, wherein component (A) comprises an epoxy resin based on glycidylamine in an amount of 1% to 30% by mass. 19. Method according to any one of claims 12 to 18, the method further comprising thickening the epoxy resin composition after impregnation.